Overall Optimization Control Strategy of Continuously Variable Transmission System

Conventional control strategy of engine optimal economic operation line and optimal dynamic operation line can’t lead to optimal performance of overall transmission system.At the aim of optimal overall performance of vehicle continuously variable transmission system,overall optimization control strategy based on power demand is studied from economic,dynamic and transient performance.Efficiency optimization algorithm is designed for whole transmission system consisted of engine,torque converter and continuously variable transmission.Best throttle opening control table,speed ratio control table and ideal state switch line of torque converter are described.In economic mode,take the highest efficiency condition meeting the power demand as the control target.In dynamic mode,take the highest power condition’s speed ratio as the control target while the throttle opening is calculated according to power demand.In transient condition,take the effective driving power of vehicle as the control object by adopting engine torque compensation and ratio shift speed limitation.Constant-power and zero-power control modes are presented.Simulation results show that,by adopting overall optimization control strategy,economical efficiency improved by 3.2%,40-80 km.h–1acceleration time reduced 13.7% and phenomenon of power fatigue under transient condition is eliminated.